Snap action device



April 17, 1962 A. v. c. DAVIS 3,030,096

SNAP ACTION DEVICE Filed March 24, 1960 INVENTOR. @2226 Z6. @ada's'.

United rates This invention relates to snap action actuators and more particularly to an accurately adjustable form thereof employing a Belleville spring as the source of stored power.

Heretofore, it has been impractical to provide accurate snap action devices employing Belleville springs due to the high inherent variations between seemingly identical springs. 7 These diiferences derive from many causes as more particularly related in my prior Patent No. 2,824,- 919 granted February 25, 1958. Among the causes of such inherent variations are variations in the metal thickness within the ranges of commercial tolerances and variations in the character of the metal itself from such factors as cold working stresses, temper and the like. In that patent there is disclosed a means by which compensation for variations in the resistance to movement of seemingly identical Belleville spring elements to bring them to snap action response to a predetermined load through the use of a second spring and adusting means therefor which spring in one construction operated in opposition to the normal bias of the Belleville spring and in another construction operated additively to the normal bias of the Belleville spring. The essential characteristic of that invention was that (a) a separate spring and adjusting means for that spring was required and (b) an entirely different construction of frame and associated members was required for each of the two forms of the device.

The present invention has for its principal object the provision of a Belleville spring having integral means by which it may be yieldingly and adjustably pro-stressed either to add to any force tending to cause the spring to move by snap action from its normal position of repose with resultant reduction of the extent of such force required to effect snap action of the Belleville spring, or to combine additively to the resistance of the Belleville spring to a snap action producing force thereon with the resultant-increase in the resistance of the Belleville spring to such force.

'Another object of the invention is to provide a snap action actuator device employing a Belleville spring and adjusting devices engaging the Belleville spring operable to optionally either increase or decrease the resistance of the Belleville spring to a snap action producing force thereon whereby the device may be adjusted for accurate, snap response to a predetermined load or force applied to the Belleville spring.

With the foregoing objects in view, together with such additional objects and advantages as may subsequently appear, the invention resides in the parts, and in the construction, combination and arrangement of parts described, by way of example, in the following specification of certain presently preferred embodiments of the invention, reference being had to the accompanying drawings which form a part of said specification, and in which drawings:

FIG. 1 is a side elevational view of a first embodiment of a Belleville spring embodying the present invention and the supporting, adjusting and motion transmitting means associated therewith,

FIG. 2 is a top plan view of FIG. 1,

FIG. 3 is a medial, sectional view on the line 3-3 of FIG. 2, I

FIG. 4 is a perspective view of the Belleville spring unit employed in the said first embodiment of the invention, i

' atent FIG. 4a is a fragmentary, sectional view taken on the line ta-4a of FIG. 2,

FIG. 5 is a side elevational view of a second embodiment of a Belleville spring embodying the present invention and the complementary supporting, adjusting and motion transmitting means therefor,

FIG. 6 is a top plan view of FIG. 5,

FIG. 7 is a medial sectional view taken on the line 7-7 of FIG. 6,

FIG. 8 is a perspective view of the said second embodiment of the Belleville spring unit in the devices as shown 5, 6, and 7, and

FIG. 9 is a graph illustrating the range of adjustment achieved by the use of the present invention.

Referring first to FIG. 4, a first form of Belleville spring of the present invention is shown, said spring comprising a spring metal coned disc 1 having a central opening bounded by an inner mounting ledge 2 and the outer periphery of said coned disc forming an outer mounting ledge 3, said outer ledge being interrupted at equal intervals by a plurality of spring arm portions 4-, 4. These arms, Lmstressed condition, first extend first, in the same direction normal to the plane of the outer periphery of said spring disc portion and thence being bent into similar curves positioning the distal ends of said arms substantially in a common plane parallel to and laterally spaced from said plane of said outer periphery of said spring disc portion. While in the instant disclosure, two of these arms are shown, it will be borne in mind that other numbers of such plurality of arms may be employed where necessary or desirable.

Next, considering FIGS. 1, 2 and 3, the spring above described is show-n in a typical mounting for achieving the adjustable snap action response to loads imposed thereon. The illustrated mounting comprises a rigid frame member 6 including a ring portion 6 having a peripheral inner shoulder '7 against which the side of the outer ledge 3 of the coned disc portion of the Belleville spring is loosely held by a snap ring 8 seated in a peripheral groove 9, said ring member 6' being cut away as at it 10 to provide clearance for the arms 4, 4. The center opening of the coned spring portion of the unit carries a'motion transmitting member 11 comprising a screw having a head 12 and a cooperating Washer 12' mounted thereon and combining with the head 12 to form a peripheral groove 13 in which the inner ledgeZ of the Belleville spring 1 is loosely contained. A nut is on the threaded shank 14' of the motion transmitting member 11 serves to hold the washer 12 against the head 12 to contain the Belleville spring in the groove 13 therebetween. The member 11 thus is disposed in-the axial line of the Belleville spring and is employed to transmit movements of the spring in response to forces applied through the trans mitting member.

An integral bridging portion 15 extends across the ring portion of the frame member 6 and is disposed in a plane between a plane containing the outer ends of the arms 4, 4 and the adjacent side of the coned disc portion of the Belleville spring 1 and said bridging portion carries a threaded stud 16 extending outwardly in the axial line of the ring 6. A nut 17 threadedly engages said stud and this nut is provided with a peripheral groove 18 in which the inner edge of the metal disc or washer 19 is loosely received, said disc having inclined openings 20, 20 through whioh the curved end portions 5, 5 of the spring arms 4, 4 extend. The length of the stud 16 is such that the extent of adjustment of the nut 17 therealong and consequently of the disc 19 mounted thereon is sufiicient either to move the ends 5, 5 of the spring arms 4, 4- to impose forces on the Belleville spring which additively oppose any forces imposed on the Belleville spring by the member 11 so that the Belleville spring will respond by snap action only to a predetermined greater force exerted by the motion transmitting member than the force to which it would respond if the arms 4, 4 were not so stressed.

Conversely, if the nut 17 is adjusted in the opposite direction (toward the bridging member 15) the washer 19 will impose stresses on the arms 4, 4 which will cause the Belleville spring portion 1 to respond to a lesser force deriving from tension on the member 11 than would be the case if the arms 4, 4 were not thus initially stressed.

Referring to FIG. 9, there is shown a graph having curves representing the load-deflection response (a) of a typical Belleville spring of the above described character in its normal response, (12) as adjusted to reduce the required load for snap action response, and (c) as adjusted to increase the required load for snap action response. It is particularly to be noted from this graph that a given spring can be thus accurately adjusted for snap action response to loads within a range in which the maximum load is approximately twice the minimum load which would be required for such response. Accordingly, a single model or form of spring may be adapted for use in a wide range of devices having a very wide nange of demands of snap action response. Furthermore, as previously mentioned, because of the nature of the adjustment, it is evident that regardless of uncontrollable variations in seemingly identical springs, the adjustment achieved by the present invention can bring all springs for a given device to an adjustment at which they respond uniformly to a very close standard of performance.

A close study of the nature of the action of the spring elements of this invention reveals that as the arms of the spring unit are stressed, these stresses are communicated in part to the coned disc area in the region of the springs with a partial deflection of those areas until the load imposed both by the stressing of the springs and through the motion transmitting element overcomes the resistance of the spring and it moves with a negative spring rate to the inherent limits of the spring itself or to such limits as may be imposed by the structure with which the spring is used.

Referring next to FIG. 8, there is shown an alternative form of Belleville spring unit 23 embodying the invention, said unit having a coned disc portion 24 provided with a central opening bounded by an inner ledge 25 and having on its outer periphery a plurality of integrally formed, laterally extending spring arms 26, 26 of the same general character as the arms 4 of the first described embodiment of the invention except that the curved portions 27, 27 of said arms diverge instead of converge.

Next, referring to FIGS. 5, 6 and 7, this spring unit is shown mounted in the same form of frame member as the first described form, wherefore, the same numbers are applied to the frame member and parts associated therewith. Also, the inner ledge of the spring is shown similarly connected to an actuating member assembly which is the same as that employed in the first embodiment, wherefore, the same numbers are employed as in the first described form of the invention. The adjusting nut 17 carries a slotted disc 28 loosely mounted in the groove 18 thereof, said disc having slots or openings 29, 29 extending there-through in which the diverging ends of the spring arms 27, 27 are slidingly received.

The effect of adjustment of the disc 28 toward and away from the frame member will bias the spring arms 26, 26 in opposite directions with respect to the Belleville spring. It is to be noted that as shown, the coned portion 24 is oppositely disposed in its normal position with respect to the normal position of the coned portion of the Belleville spring 1 in the first embodiment. Adjusting the disc 28 toward the frame member will produce a yielding bias on the arms 26, 26 which combines with any force deriving from compression forces on the member 11 to overcome the resistance of the spring to such forces, and therefore a lesser force will be required to cause snap action of the spring. Conversely, moving the disc 28 outwardly away from the frame member will move the arms to increase the resistance of the coned portion 24 of the Belleville spring to the forces applied by the member 11. In other words, due to the fact that the arms 26, 26 are oppositely disposed with respect to the coned disc portion of the unit, an adjustment in the same direction along the stud i6 produces opposite results.

It will be understood, however, that either of the two forms of Bellcville spring unit may have the coned portion thereof extending either toward or away from the bridging member as may be deemed most satisfactory for an intended use of the device. In both forms of springs the capability of a very wide range of adjustment for a Belleville spring formed as a unit may be achieved.

Actuators of the above character may be employed for various uses in which snap action response to applied forces is desired. Representative of such uses are force responsive devices such as pressure switches, limit switches, valves, etc., but the recitation of such representative uses shall be deemed to be by way of description and not of limitation.

It is appreciated that in the light of the foregoing specification, changes and modifications will suggest themselves to others skilled in the art to which the invention appertains. Accordingly, the invention is not to be deemed to be limited to the precise presently preferred embodiments which have been disclosed in the foregoing specification by way of example, and it will be understood that the invention includes as well all such changes and modifications in the parts and in the construction, combination and arrangement of parts as shall come within the purview of the appended claims.

I claim:

1. A cone disc snap action spring device responsive to loads imposed in a direction parallel to the axial line of the cone disc; said device comprising a coned spring disc portion having a snap action characteristic and having a plurality of integrally formed spring arms equally spaced about the outer periphery of said spring disc portion and extending first generally in the same direction normal to the plane of the outer periphery of said spring disc portion and thence being bent in similar curves positioning the distal ends of said arms substantially in a common plane parallel to and laterally spaced from said plane of said outer periphery of said spring disc portion.

2. A snap action device as claimed in claim 1 in which said distal ends of said spring arms extend toward said axial line of said spring disc portion.

3. A snap action device as claimed in claim 1 in which said distal ends of said spring arms extend away from said axial line of said spring disc portion.

4. In a snap action device a spring element having a coned spring disc portion having a snap action characteristic and having a plurality of integrally formed spring arms equally spaced about the outer periphery of said coned spring disc portion and extending first generally parallel to the axial line of said coned disc portion and thence curving into distal ends extending substantially at right angles to said axial line and in lines extending radially of said axial line, and adjusting means engagcable with said spring arms movable in a direction parallel to the axial line of said spring disc portion to bias said spring arms simultaneously and uniformly to vary the load responsive snap action of said coned spring disc portion of said spring element.

5. A snap action device including a frame member, a snap action spring element mounted on said frame memher and including a coned spring disc portion having a snap action characteristic and having a plurality of integrally formed spring arms equally spaced about the outer periphery of said coned spring disc portion and extending first generally in the same direction normal to the plane of said outer periphery of said spring disc portion and thence being bent into similar curves positioning the distal ends of said arms substantially in a common plane parallel to and laterally spaced from said plane of the outer periphery of said spring disc portion and adjusting means mounted on said frame member and engaging said spring arms; said adjusting means being variable in the axial line of said spring disc portion to vary the load required to efiect snap action response of said spring element to loads applied thereon.

6. A snap action device as claimed in claim 5 in which said adjusting means comprises a threaded stud disposed in the axial line of said coned disc portion of said spring 19 2,806,918

element and extends from the side of said frame member adjacent to said spring arms, a nut on said threaded stud, and a disc freely mounted on said nut and having slots extending therethrough in which said distal ends of said 5 arms are slidingly received.

References Cited in the file of this patent UNITED STATES PATENTS Spencer July 20, 1926 Lautzenhiser Sept. 17, 1957 

